Jack Straw, the former justice secretary, has rejected a demand from a US senate committee to appear in Washington next week to answer questions about the release of the man convicted of the Lockerbie bombing.

As Labour MPs accused the senators of "grandstanding", Straw wrote to the chairman of the senate committee to decline his "kind invitation" on the grounds that he played no role in the release of Abdelbaset al-Megrahi.

A transatlantic row blew up on Thursday night after Straw and Kenny MacAskill, the Scottish justice minister, were asked to appear before the senate foreign relations committee which is investigating the release of al-Megrahi. Senators are trying to establish whether a $900m (£590m) oil exploration deal signed by BP and Libya "directly or indirectly influenced" the decision to release Megrahi.

MacAskill, who released al-Megrahi on compassionate grounds last August, declined the invitation on Thursday. Straw demonstrated his irritation earlier today by pointing out that senators were seeking to attract attention ahead of the mid-term elections in November.

The committee summoned Straw because he was involved in drawing up a prisoner transfer agreement between Britain and Libya. In a letter to Senator Robert Menendez, Straw said the prisoner transfer agreement was irrelevant because al-Megrahi was released on compassionate grounds under Scottish law.

"I had absolutely nothing to do with [the] decision," Straw wrote. "Indeed I was on holiday at the time and only learned about it from an item on the BBC News website. It follows that I do not see how I could help your committee 'understand several questions still lingering from this decision' … You will therefore excuse me if I do not accept your kind invitation."

Alex Salmond, the Scottish first minister, explaining why MacAskill would not appear before the committee, told Radio 4: "We are not responsible to the US senate and its committees. It would be totally unprecedented for serving ministers in any government to appear before the committee of another parliament."

Mike Gapes, the Labour chairman of the foreign affairs select committee in the last parliament, attacked the decision to invite Straw. "We, in our parliament, have never tried to summon Colin Powell or Condoleezza Rice. I think it is political grandstanding by some US senators."

Sir Christopher Meyer, the former British ambassador to Washington, endorsed the decisions by Straw and MacAskill. "As a matter of principle a British government or a Scottish government should not submit to the jurisdiction of an American congressional committee," Meyer told Radio 4.

"That does not mean that they can't in some way co-operate with the committee's enquiry, either privately or in correspondence. It is what the Americans would do if the boot was on the other foot. They have done it already. A number of them were approached to give evidence to the Chilcot inquiry. They declined to do so. But they have co-operated in private. I just don't think it is right for members of a sovereign government, albeit a very close ally, to be required in public under oath to give evidence to an American congressional inquiry."

Kevan Jones, a former Labour defence minister, said: "The senate committee clearly is on a witch-hunt against BP. They would be highly annoyed if one of our select committees demanded to see an American politician put before us. They need to be careful because they are trying the patience of good friends of the US. I include myself as one."